Method and apparatus for dynamic media access control in a multiple access system

ABSTRACT

An electronic device may be operable to control access to a physical medium (e.g., airwaves, a copper cable, or an optical fiber) utilizing carrier sense multiple access (CSMA). The amount of time that the electronic device must sense the physical medium as being inactive before it permits transmission of a message onto the physical medium may be determined based on: the size of the message, the type of the message, the symbol rate at which the message is to be transmitted, and/or a channel onto which the message is to be transmitted. Similarly, other aspects of how and when electronic device transmits and/or receives on the physical medium may be controlled via one or more dynamically configurable parameters which may be configured based on characteristics of received and/or to-be-transmitted messages.

CLAIM OF PRIORITY

This patent application makes reference to, claims priority to andclaims benefit from U.S. Provisional Patent Application Ser. No.61/464,376 entitled “Advanced Communication System for Wide-area LowPower Wireless Applications and Active RFID” and filed on Mar. 2, 2011.

The above-referenced application is hereby incorporated herein byreference in its entirety.

INCORPORATION BY REFERENCE

This patent application also makes reference to:

U.S. Provisional Patent Application Ser. No. 61/464,376 titled “AdvancedCommunication System for Wide-Area Low Power Wireless Applications andActive RFID” and filed on Mar. 2, 2011;U.S. Provisional Patent Application Ser. No. 61/572,390 titled “Systemfor Adding Dash7-Based Applications Capability to a Smartphone” andfiled on Jul. 15, 2011;U.S. patent application Ser. No. 13/267,640 titled “Method and Apparatusfor Adaptive Searching of Distributed Datasets” and filed on Oct. 6,2011;U.S. patent application Ser. No. 13/267,621 titled “Method and Apparatusfor Low-Power, Long-Range Networking” and filed on Oct. 6, 2011;U.S. patent application Ser. No. 13/270,802 titled “Method and Apparatusfor a Multi-band, Multi-mode Smartcard” and filed on Oct. 11, 2011;U.S. patent application Ser. No. 13/270,959 titled “Method and Apparatusfor an Integrated Antenna” and filed on Oct. 11, 2011;U.S. patent application Ser. No. 13/289,054 titled “Method and Apparatusfor Electronic Payment” and filed on Nov. 4, 2011;U.S. patent application Ser. No. 13/289,050 filed on Nov. 4, 2011;U.S. patent application Ser. No. 13/297,348 titled “Method and Apparatusfor Interfacing with a Smartcard” and filed on Nov. 16, 2011;U.S. patent application Ser. No. 13/354,513 titled “Method and Apparatusfor Memory Management” and filed on Jan. 20, 2012;U.S. patent application Ser. No. 13/354,615 titled “Method and Apparatusfor Discovering, People, Products, and/or Services via a LocalizedWireless Network” and filed on Jan. 20, 2012;U.S. patent application Ser. No. 13/396,708 titled “Method and apparatusfor Plug and Play, Networkable ISO 18000-7 Connectivity” and filed onFeb. 15, 2012;U.S. patent application Ser. No. 13/396,739 titled “Method and Apparatusfor Serving Advertisements in a Low-Power Wireless Network” and filed onFeb. 15, 2012;U.S. patent application Ser. No. ______ (Attorney Docket No. 24665US02)titled “Method and Apparatus for Forward Error Correction (FEC) in aResource-Constrained Network” and filed on Feb. 29, 2012;U.S. patent application Ser. No. ______ (Attorney Docket No. 24666US02)titled “Method and Apparatus for Adaptive Traffic Management in aResource-Constrained Network” and filed on Feb. 29, 2012;U.S. patent application Ser. No. ______ (Attorney Docket No. 24668US02)titled “Method and Apparatus for Rapid Group Synchronization” and filedon Feb. 29, 2012;U.S. patent application Ser. No. ______ (Attorney Docket No. 24669US02)titled “Method and Apparatus for Addressing in a Resource-ConstrainedNetwork” and filed on Feb. 29, 2012;U.S. patent application Ser. No. ______ (Attorney Docket No. 24670US02)titled “Method and Apparatus for Query-Based Congestion Control” andfiled on Feb. 29, 2012; andU.S. patent application Ser. No. ______ (Attorney Docket No. 24671US02)titled “Method and Apparatus for Power Autoscaling in aResource-Constrained Network” and filed on Feb. 29, 2012.

Each of the above-referenced applications is hereby incorporated hereinby reference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to networking. Morespecifically, certain embodiments of the invention relate to a methodand apparatus for dynamic media access control in a multiple accesssystem.

BACKGROUND OF THE INVENTION

Existing methods of media access control for a shared communicationmedium are often inefficient. Further limitations and disadvantages ofconventional and traditional approaches will become apparent to one ofskill in the art, through comparison of such systems with some aspectsof the present invention as set forth in the remainder of the presentapplication with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method is provided for dynamic media access control in amultiple access system, substantially as illustrated by and/or describedin connection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts exemplary communication devices which may comprise adynamically adaptable media access controller.

FIG. 2 is a diagram illustrating aspects of the invention taking placeat different layers of the OSI model.

FIGS. 3A-3C are a flowchart illustrating the use of dynamic CSMA forcommunicating over a shared physical medium.

FIG. 4A is a flowchart illustrating hold-state or idle-state operationof an electronic device.

FIG. 4B is a flowchart illustrating receive-state operation of anelectronic device.

FIG. 5A is a flowchart illustrating the determination of guard time fora CSMA process based on a type of message to be transmitted.

FIG. 5B is a flowchart illustrating the determination of guard time fora CSMA process based on a rate at which a message is to be transmitted.

FIG. 5C is a flowchart illustrating the determination of guard time fora CSMA process based on a length of a message to be transmitted.

FIGS. 6A-6D depict data structures which may be utilized forimplementing dynamic media access control algorithms.

FIG. 7 depicts an exemplary file system in a device comprising adynamically adaptable media access controller.

FIG. 8 is a flowchart illustrating exemplary steps for channel scanningin a device comprising a dynamically adaptable media access controller.

FIG. 9 is a flowchart illustrating exemplary steps for beacontransmission by a device comprising a dynamically adaptable media accesscontroller.

FIGS. 10A-10C illustrate generation of parameters utilized by adynamically adaptable media access controller.

FIG. 11A illustrates the structure of an exemplary physical layer framecontaining a first type of data link layer protocol data unit (PDU).

FIG. 11B illustrates the structure of an exemplary physical layer framecontaining a second type of data link layer protocol data unit (PDU).

FIG. 12A illustrates the structure of an exemplary first type ofnetwork-layer PDU.

FIG. 12B illustrates the structure of an exemplary second type ofnetwork-layer PDU.

FIG. 13 depicts the structure of an exemplary transport-layer PDU.

FIGS. 14A-14E depict the structure of exemplary portions of atransport-layer PDU.

FIGS. 15A-15F depict the structure of exemplary portions of atransport-layer PDU.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As utilizedherein, “and/or” means any one or more of the items in the list joinedby “and/or”. As an example, “x and/or y” means any element of thethree-element set {(x), (y), (x, y)}. As another example, “x, y, and/orz” means any element of the seven-element set {(x), (y), (z), (x, y),(x, z), (y, z), (x, y, z)}. As utilized herein, the terms “block” and“module” refer to functions than can be implemented in hardware,software, firmware, or any combination of one or more thereof. Asutilized herein, the term “exemplary” means serving as a non-limitingexample, instance, or illustration. As utilized herein, the terms“e.g.,” and “for example,” introduce a list of one or more non-limitingexamples, instances, or illustrations.

FIG. 1 depicts exemplary communication devices which may comprise adynamically adaptable media access controller. Shown in FIG. 1 aredetails of an exemplary first device 102 and details of an exemplarysecond device 104.

The CPU 204 may comprise circuitry operable to control operation of thefirst device 102. The CPU 204 may, for example, execute an operatingsystem and/or other programs such (e.g., programs that enable a userinterface of the device 102). The CPU 204 may generate one or morecontrol signals for controlling the operation of the device 102. The CPU204 may, for example, control a mode of operation of the device 102.

The CPU 214 may comprise circuitry operable to control operation of thesecond device 104. In some instances, the CPU 214 may be substantiallysimilar to the CPU 204. In instances that the device 102 is lessresource-constrained device, such as a base station or networkcontroller, and the device 104 is more resource-constrained device, suchas a battery-powered tag or a smartcard as described inabove-incorporated U.S. patent application having Ser. No. 13/270,802,the CPU 204 may be less-complex (e.g., comprise fewer gates, utilizeless power, utilize less memory, etc.) than the CPU 214. In oneembodiment, for example, the CPU 204 may comprise a RISC or ARMprocessor, and the CPU 214 may comprise a state-machine having arelatively small number of states (e.g., four states).

The radio 207 may comprise a processor 208 and an analog front-end (AFE)209. The processor 208 may comprise circuitry operable to interface withthe AFE 209 to receive and transmit data, and to process received andto-be-transmitted data. For transmission, the processor 208 may beoperable to receive data from the CPU 204 and/or memory 206, encode,packetize, and/or otherwise process the data to prepare it fortransmission in accordance with one or more wireless protocols, andoutput the data to the AFE 209 for transmission. For reception, theprocessor 208 may be operable to receive data via the AFE 209, processthe received data and output received data to the memory 206 and/or theCPU 204. Exemplary protocols which may be supported by the second device104 include the ISO 18000-7 standard, and protocols described in theabove-incorporated U.S. Provisional Patent Application having Ser. No.61/464,376 filed on Mar. 2, 2011.

The radio 217 may comprise a processor 218 and an analog front-end (AFE)219. The baseband processor 218 may comprise circuitry operable tointerface with the AFE 219 to receive and transmit data, and to processreceived and to-be-transmitted data. In some instances, the basebandprocessor 218 may be substantially similar to the baseband processor208. In instances that the device 102 is less-resource-constraineddevice, such as a base station or network controller, and the device 104is a more-resource-constrained device, such as a battery-powered tag,the baseband processor 218 may be less-complex (e.g., comprise fewergates, utilize less power, utilize less memory, etc.) than the basebandprocessor 208. In one embodiment, for example, the baseband processor208 may be operable to implement more complex signal processingalgorithms (e.g., FEC decoding) than the baseband processor 218.

The analog front-end (AFE) 209 may comprise circuitry suitable forprocessing received and/or to-be-transmitted data in the analog domain.For transmission, the AFE 209 may receive digital data from the basebandprocessor 208, process the data to generate corresponding RF signals,and output the RF signals to the antenna 210. For reception, the AFE 209may receive RF signals from the antenna 210, process the RF signals togenerate corresponding digital data, and output the digital data to thebaseband processor 209. In some instances, the AFE 219 may besubstantially similar to the AFE 209. In instances that the device 102is less-resource-constrained device, such as a base station or networkcontroller, and the device 104 is a more-resource-constrained device,such as a battery-powered tag, the AFE 219 may be less-complex (e.g.,comprise fewer gates, utilize less power, utilize less memory, etc.)than the AFE 209. In one embodiment, for example, the AFE 209 maycomprise a more-sensitive receiver, a more powerful transmitter than theAFE 219.

Circuitry of the memory 206 may comprise one or more memory cells andmay be operable to store data to the memory cell(s) and read data fromthe memory cell(s). The one or more memory cell may comprise one or morevolatile memory cells and/or one or more non-volatile memory cells. Thememory 206 may store data arranged, for example, as an indexed shortfile block (ISFB) and/or indexed short file series block (ISFSB) asdescribed in the above-incorporated U.S. Provisional Patent Applicationhaving Ser. No. 61/464,376.

Circuitry of the memory 216 may comprise one or more memory cells andmay be operable to read data from the memory cell(s) and/or store datato the memory cell(s). The memory 216 may store data arranged, forexample, as an indexed short file block (ISFB) and/or indexed short fileseries block (ISFSB) as described in the above-incorporated U.S.Provisional Patent Application having Ser. No. 61/464,376. In someinstances, the memory 216 may be substantially similar to the memory206. In instances that the device 104 is resource-constrained, thememory 216 may be less-complex (e.g., comprise fewer gates, utilize lesspower, etc.) than the memory 206.

Each of the clocks 211 and 221 may be operable to generate one or moreoscillating signals which may be utilized to control synchronouscircuitry of the device 100. Each of the clocks 211 and 221 maycomprise, for example, one or more crystal oscillators, phase-lockedloops, and/or direct digital synthesizers. Each of the clocks 211 and221 may also comprise a “date/time” or “real-time” clock operable tokeep track of time of day, day of week, day of month, month, and/oryear.

The interfaces 212 and 222 may enable configuring and/or programming thedevices 102 and 104, respectively. In an exemplary embodiment, one ormore values of one or more timing parameters may be programmed via theprogramming interfaces 212 and/or 222.

Each of the antennas 210 and 220 may be operable to transmit and receiveelectromagnetic signals in one or more frequency bands. In an embodimentof the invention, the antennas 210 and 220 may be operable to transmitand receive signals in the ISM frequency band centered at 433.92 MHz.

In operation, the device 102 may be, for example, a base station ornetwork controller, and the device 104 may be a mobile device such as asmart phone or a smartcard. The devices 102 and 104 may communicate viathe radios 207 and 217. In communicating over the physical medium (e.g.,the airwaves for wireless communication or a cable for wiredcommunication), values of one or more media access control (MAC)parameters that control when and/or how to access the physical mediummay be dynamic (i.e., configured “real-time” or “on-the-fly”). Forexample, values of one or more MAC parameters may be changed on aper-message and/or per-dialog (an exchange of one or morelogically-related messages) basis. Exemplary MAC parameters whose valuesmay be dynamically determined include: which channel(s) to transmitand/or receive on, whether to utilize CSMA, how long to listen beforetransmitting, how long to listen after transmitting, and/or how long achannel must be free before transmitting on that channel. Parametervalues may, for example, change based on the contents of a messagereceived over the medium and/or based on instructions stored locally(e.g., in memory 216 for the device 104). Such instructions may, forexample, be generated by an application and/or operating system runningon the device 102 and/or 104.

FIG. 2 is a diagram illustrating aspects of the invention taking placeat different layers of the OSI model. As shown in FIG. 2, the device 104may comprise: a congestion module 230 and/or a flow control module 232which may operate at the transport layer (layer 4 of the OSI model); acarrier sense multiple access (CSMA) module 236 which may operate at thedata link layer (layer 2 of the OSI model); and a received signalstrength indicator (RSSI) module which may operate at the physical layer(layer 1 of the OSI model). The device 104 may also comprise a register234 which may be readable and/or modifiable by the congestion controlmodule 230, the flow control module 232, and/or the CSMA module 236.

In operation, the device 104 may receive a request message and decide totransmit a response message in reply to the request message. For thetransmission of the response message, the congestion control module 230may receive a parameter T_(CA0), a parameter T_(G), a parameterCSMA_options, and a parameter ch_list. The parameters may be utilizeddirectly in controlling access to the physical medium and/or utilizedfor determining values of other parameters which, in turn, may beutilized in controlling access to the physical medium. One or more ofthe parameters may have been received in, and/or derived from,information contained in the received request message. In this manner,the requesting device may control, at least in part, if, how, and/orwhen the responding device 104 transmits a response to the request.

The parameter ch_list may comprise a list of channel identifiers, whereeach channel identifier is uniquely associated with a particularcombination of center frequency and bandwidth. The list of channels maycorrespond to channels on which the requesting device (i.e., the devicethat sent the request message) will listen for responses. The congestioncontrol module 230 may modify the parameter ch_list to generate ch_list′which may then be passed onto the CSMA module 236. The modification ofch_list to generate ch_list′ may be, for example, to remove one or morechannels from the list because the device 104 is aware that the removedchannel is highly congested, the device 104 does not support thechannel, and/or for some other reason.

The parameter T_(CA0) may correspond to the amount of time that thedevice 104 has to begin transmitting the response message onto thephysical medium. In an exemplary embodiment, T_(CA0) may correspond toT_(C)−T_(resp), where the value of T_(C) (“contention period” or“response timeout”) is the amount of time that the requesting device isgoing to listen for responses to the request message (T_(C) may havebeen received in the request message), and T_(resp) is the amount oftime it will take the device 104 to transmit the response message.

The parameter CSMA_options may indicate whether to utilize carrier sense(i.e., whether to “listen before talk”) and/or which equations and/oralgorithms the device 104 should utilize for calculating values for oneor more timing parameters utilized by the CSMA module 236 and/or thecongestion control module 230. Two exemplary parameters which may becalculated are T_(G)′ (“guard time) and T_(CA) (“collision avoidancetimeout”). To illustrate, in an exemplary embodiment, T_(CA) may be setequal to T_(CA0) for a first value of CSMA_options, but T_(CA) may beset equal to T_(CA0)/2 for a second CSMA_options. Other factors mayadditionally or alternatively be used for calculating T_(CA). Suchfactors may comprise, for example, characteristics (e.g., type and/orlength) of the response message, and/or characteristics (e.g., datarate, frequency, bandwidth, modulation type, and/or symbol rate) of thechannel onto which the response message is to be transmitted. Aftercalculating T_(CA), the congestion control module 230 may store thevalue of T_(CA) in the register 234.

The parameter T_(G) may be an initial value for a parameter T_(G)′(“guard time”). T_(G)′ which may determine how long the device 104 mustsense the physical medium as being inactive before the device 104 beginstransmitting the response message onto the physical medium. Otherfactors in determining a value of T_(G)′ may include CSMA_options,T_(CA), T_(CA0), characteristics (e.g., type and/or length) of theresponse message, and/or characteristics (e.g., data rate, frequency,bandwidth, modulation type, and/or symbol rate) of the channel ontowhich the response message is to be transmitted.

Upon initialization from the congestion control module 230, the CSMAmodule 236 may perform CSMA as, for example, described below inreference to FIG. 3C. If an available channel is detected, the CSMAmodule 236 may assert TxEN and the flow control module 232 may thenmanage the transmission of the response packet onto the medium on theavailable channel. Upon TxEN being asserted, the flow control module 232may modify the value stored in the register 234. If, after trying for aperiod of time equal to T_(CA), none of the channels in the channel listare determined to be available, then, depending on the value of T_(CA),the device 104 may abort transmission of the response or may take abreak and try again later. For example, if the congestion control modulesets T_(CA)=T_(CA0) then upon the CSMA failing to obtain access to themedium for a period of time T_(CA), the device 104 may aborttransmission of the response message. Conversely, if T_(CA)<T_(CA0),then the congestion control module 230 may wait for a period of timeT_(wait), and then trigger the CSMA module 236 to once again attempt togain access to the medium. The second attempt may last for up to aperiod of time equal to T_(CA0)−T_(CA)−T_(wait). Factors in determininga value of T_(wait) may include CSMA_options, T_(CA), T_(CA0),characteristics (e.g., type and/or length) of the response message,and/or characteristics (e.g., data rate, frequency, bandwidth,modulation type, and/or symbol rate) of the channel onto which theresponse message is to be transmitted.

FIGS. 3A-3C are a flowchart illustrating the use of dynamic CSMA forcommunicating over a shared physical medium. Referring to FIG. 3A, theexemplary steps begin with step 302 in which the device 102 generates arequest message. The message may, for example, comprise a query templateand seek responses from devices which possess certain characteristicsand/or store certain data.

In step 304, the device 102 determines a value of one or more parametersthat instruct devices receiving the request as to if, how, and/or whento send responses to the request message. For example, the device 102may determine a value of T_(C) (the amount of time it will listen forresponses to the request), CSMA_options (a flag which indicates anequation and/or algorithm that responding devices should use whencalculating values for certain timing parameters), and a list of one ormore channels on which the device 102 will listen for responses. Thedevice 102 may determine T_(C), CSMA_options, and/or the channel listbased on, for example: the type of request, the symbol rate of thechannel(s) over which the request will be transmitted and/or responsesreceived, the results of past requests (e.g., knowledge about thedevices that have responded to past requests), the location of thedevice 102 (e.g., based on received GPS signals, other wireless signals,and/or user input), the number or responses that are desired, and/or anyother suitable criteria. For example, the device 102 may set T_(C) to alarger value if it wants to receive many and/or long responses, and mayset T_(C) to a smaller value if it wants to receiver fewer and/orshorter responses.

In step 306, the device 102 inserts the value(s) of the one or moreparameters calculated in step 304 into one or more fields of the requestmessage. In step 308, the device 102 transmits the request message. Inan exemplary embodiment, the device 102 may perform CSMA and transmitthe request message only upon sensing that the medium is free. In suchinstances, timing parameters utilized as part of the CSMA process may bethe same as the values calculated for the potential response messages,or may be different. For example, first values of timing parameters,such as T_(CA) and T_(G)′, may be utilized when transmitting requestmessages whereas second values of timing parameters, such as T_(CA) andT_(G)′, may be utilized when transmitting response messages. In anotherexemplary embodiment, for request messages, the device 102 may not sensewhether another device is already transmitting because, for example, itmay not care whether a collision occurs or may know (e.g., throughscheduling) that the medium is free.

In step 310, the request message is received by the device 104. In step312, the device 104 processes the received request message and decidesto transmit a response message. In step 314, the device 104 determinevalues of T_(CA) and T_(G)′ to be utilized for transmitting the responsemessage. The value of T_(CA) for the response message may be calculated,for example, as described above with respect to FIG. 2. The value ofT_(G)′ for the response message be calculated as, for example, describedbelow with respect to FIGS. 5A-5C.

Referring now to FIG. 3B, in step 316 it is determined whether the valueof T_(CA) calculated in step 314 is compared to a threshold. If thevalue of T_(CA) is less than a threshold (i.e., the requesting devicewill cease listening before the complete response message can betransmitted) then in step 318, the device 104 aborts transmission of theresponse message.

Returning to step 316, if the value of T_(CA) is greater than thethreshold, then, in step 320, the congestion control module 230 triggersthe CSMA process performed by the CSMA module 236. In step 322, the CSMAprocess described below with respect to FIG. 4B takes place. In step324, if transmission was successful (i.e., either CSMA was disabled oran available channel for transmitting the response message was detectedduring step 322), then the exemplary steps advance to step 330. In step330, the flow control module 232 sets the T_(CA) register 234 to a valueguaranteed to be less than the threshold utilized in step 316. Forexample, the flow control module 232 may set the T_(CA) register 234 toa value of −1.

Returning to step 324, if the step 322 did not result in a successfultransmission, then the exemplary steps advance to step 326. In step 326,the congestion control module counts down an amount of time T_(wait).The value of T_(wait) may be calculated based on variety of factors suchas, for example, CSMA_options, T_(CA0), T_(CA), T_(G)′, the length ofthe response message, the type (e.g., foreground or background) of theresponse message, the symbol rate at which the response message is to betransmitted, and/or a search score generated by comparing a receivedsearch token with locally stored data.

In step 328, the value stored in the T_(CA) register 234 is updated. Inan exemplary embodiment, the value stored in the register 234 may beupdated by subtracting off the amount of time that has elapsed since thevalue was calculated. In another exemplary embodiment, a new value ofT_(CA) may be calculated based on, for example, CSMA_options, T_(G),′and/or on how much time is left in the contention period (the timeperiod of duration T_(C) during which the requesting device will listenfor responses).

Referring now to FIG. 3C, in step 342, if CSMA is disabled (i.e., thedevice 104 is configured to transmit onto the medium without firstsensing whether another device is currently transmitting) then the stepsadvance to step 356. In step 356, the CSMA module 236 asserts TxEN. Instep 358 the message is transmitted by the flow control module 232.

Returning to step 342, if CSMA is enabled, then in step 344, a variablei is set to 1. In step 346, the physical layer receiver of the device104 is powered-up and configured to receive on the i^(th) channelidentified by the parameter ch_list′. In step 348, the CSMA module 236detects whether CS from the physical layer is asserted. The PHY mayassert CS when the received signal strength is above a threshold. Thethreshold utilized by the RSSI module 238 may have been pre-configuredby an administrator and/or configured dynamically based on, for example,past performance and/or based on information contained in the receivedrequest message. If CS is not asserted, then in step 350, the CSMAmodule 236 waits for a period of time equal to T_(G)′. In step 352, theCSMA module 236 again detects whether CS from the physical layer isasserted. If CS is not asserted then, in step 356 the CSMA module 236asserts TxEN. In step 358 the flow control module 232 manages thetransmission of the response message onto the physical medium.

Returning to steps 348 and 352, if either of these steps detect that CSis asserted, then the exemplary steps advance to step 362. In step 362,the variable i is incremented by 1. In step 364, the value of T_(CA) inregister 236 is updated by subtracting off the amount of time that haselapsed since the register was last programmed. In step 366, the updatedvalue of T_(CA) is compared to a threshold (i.e. it is determinedwhether there would still be time to transmit the response messagebefore the contention period ends). If not, then in step 370, TxENremains deasserted and the steps advance to step 360. If so, then instep 368 it is determined whether all channels in the channel list havebeen checked for availability. If not, then the exemplary steps returnto step 346. If all channels have been checked, then the exemplary stepsadvance to step 370.

FIG. 4A is a flowchart illustrating hold-state or idle-state operationof an electronic device. The exemplary steps begin with step 402 whenthe device 104 enters an idle or hold state of operation. In step 404,the device 104 determines values of one or more MAC parameters such as,for example, Channel ID, scan duration (T_(SD)), and time-to-next-scan(T_(NS)). In step 406, upon the triggering of a scan (e.g., based on avalue of T_(NS) and/or a real-time clock) a physical layer receiver ofthe device 104 is powered-up and configured to listen on the channelindicated by the value of Channel ID determined in step 404. In step408, if the device listens for T_(SD) without CS being asserted, thenthe exemplary steps advance to step 410. In step 410, the device 104waits an amount of time equal to T_(NS) before returning to step 404. Onthe other hand, in step 408, if CS is asserted before T_(SD) times out,then the device 104 may transition to a receive state of operation as,for example, described with respect to FIG. 4B.

FIG. 4B is a flowchart illustrating receive-state operation of anelectronic device. The steps begin with step 414 when the device 104enters a receive state of operation. In step 416 the device may receivea number of bits which may constitute all or part of a frame. In step418, the device 104 may compare at least a portion of the received bitsto one or more known values. The result of the comparison may indicatewhether the bits received in step 418 were part of a valid frame and, ifso, the type of frame. For example, a valid frame may begin with aplurality of bits that constitute a sync word. Accordingly, the device104 may compare the initial plurality of bits to one or more known-goodvalues of the sync word. If the initial plurality of bits is not a validsync word, then the received bits may be discarded and the devicereturns to an idle or hold state of operation. If the initial pluralityof bits is a valid sync word, then the exemplary steps advance to step420.

In step 420, the device may receive any remaining bits of the frame. Instep 422, the device 104 may parse one or more fields of the receivedframe to determine whether the device 104 was an intended recipient ofthe frame and/or whether the device 104 cares about the frame (i.e.,wants to devote resources to further processing the message). Frames notintended for the device 104 and/or not of interest to the device 104 maybe discarded without further processing. In step 424, if there areadditional frames to be received then the steps may return to step 420.If there are no additional frames to receive then in step 426 the device104 may determine whether the received packet passes (i.e. is notdropped during) MAC filtering. If not, then the device 104 may return tostep 408 in which it may re-evaluate T_(SD) and reinitialize reception.If so, then the device 104 may transition to a transmit state (e.g., asdescribed in portions of FIGS. 4A-4C).

FIG. 5A is a flowchart illustrating the determination of guard time fora CSMA process based on a type of message to be transmitted. Theexemplary steps begin with step 502 when the device 104 has a frame totransmit. In step 504 the device 104 may determine whether the frame tobe transmitted is a first type of frame (e.g., a foreground frame) or asecond type of frame (e.g., a background frame). If the frame is of thefirst type, then in step 506 T_(G)′ may be set to a first value. If theframe is of the first type, then in step 506 T_(G)′ may be set to asecond value, which may be higher than the first value.

FIG. 5B is a flowchart illustrating the determination of guard time fora CSMA process based on a symbol rate at which a message is to betransmitted. The exemplary steps begin with step 510 when the device 104has a frame to transmit. In step 512 the device 104 may determinewhether the frame to be transmitted at a first symbol rate (e.g., 200kS/s) or at a second symbol rate (e.g., 55.55 kS/s). If the frame is tobe transmitted at the first symbol rate, then, in step 514, T_(G)′ maybe set to a first value. If the frame is to be transmitted at the secondsymbol rate, then in step 506 T_(G)′ may be set to a second value, whichmay be higher than the first value.

FIG. 5C is a flowchart illustrating the determination of guard time fora CSMA process based on a length of a message to be transmitted. Theexemplary steps begin with step 520 when the device 104 has a frame totransmit. In step 522 the device 104 may determine whether the length ofthe frame to be transmitted is below or above a threshold. If the lengthof the frame is less than the threshold, then, in step 524, T_(G)′ maybe set to a first value. If the length of the frame is greater than thethreshold, then, in step 526, T_(G)′ may be set to a second value, whichmay be higher than the first value.

Although FIGS. 5A-5C illustrate scenarios selecting between two valuesof T_(G)′, in practice values of T_(G)′ may be selected from a largerset of options such that T_(G)′ could be controlled with moregranularity.

FIGS. 6A-6D depict data structures which may be utilized forimplementing dynamic media access control algorithms.

Referring to FIG. 6A, there is shown a scan n-tuple (a four-tuple) 602comprising a Channel ID field 604 ₁, a scan type field 604 ₂, a scanduration field 604 ₃, and a time-to-next-scan field 604 ₄. The ChannelID field 604 ₁ may indicate a frequency and/or bandwidth of a channel onwhich to listen for traffic. The scan type field 604 ₂ may determine thetype of frame(s) to listen for (e.g., background or foreground frames).The scan duration field 604 ₃ may indicate how long to listen to thechannel. The time-to-next scan field 604 ₄ may indicate how long to waitbetween listening to the channel identified in scan n-tuple 602 andlistening to a channel identified in another scan n-tuple.

Referring to FIG. 6B, there is shown an exemplary sequence 606 of scann-tuples 602 ₁-602 _(M), where M is an integer. Each of the scann-tuples 602 ₁-602 _(M) in the sequence 606 may be as described withrespect to FIG. 6A.

In operation, upon entering an idle state of operation (e.g., at a timetriggered by a real-time clock), the device 104 may read the first scann-tuple 602 ₁, listen to the channel identified by field 604 ₁ of scann-tuple 602 ₁ for the type of frame identified in field 604 ₂ of scann-tuple 602 ₁. The device 104 may begin counting-down the amount of timein field 604 ₄ while concurrently beginning listening for the amount oftime in field 604 ₃. After the longer of these two time fields expires,the device 104 may read the next scan n-tuple 602 ₂ in the sequence 606and operate accordingly, that is, enter a listen state followed by await state according to the fields of the scan n-tuple 602 ₂. The device104 may repeat this process until it has operated in accordance witheach of the scan n-tuples 602 ₁-602 _(M). After completing the scandescribed in the last n-tuple of the sequence 606, the device may returnto the first n-tuple in the sequence 614.

Referring to FIG. 6C, there is shown a beacon n-tuple (a six-tuple) 610comprising a Channel ID field 612 ₁, a CSMA options field 612 ₂, apointer 612 ₃, a contention period duration (T) field 612 ₄, aredundancy count field 612 ₅, and a time-to-next-beacon field 612 ₅. TheChannel ID field 612 ₁ may indicate a frequency and/or bandwidth of achannel on which to transmit a beacon. The CSMA options field 612 ₂ mayindicate if responses should utilize CSMA when responding and, if so,how they should determine parameters for performing the CSMA. Thepointer field 612 ₃ may point to a file or block of data that is to betransmitted as part of the beacon (e.g., transmitted as the payload of aframe). The contention period duration field 612 ₄ may indicate how longthe device should listen for responses to the beacon. The redundancycount field 612 ₅ may indicate how many times the beacon transmissionshould be repeated. The time-to-next beacon field 612 ₆ may indicate howlong to wait between transmitting the beacon described in beacon n-tuple610 and transmitting a beacon described in another beacon n-tuple.

Referring to FIG. 6D, there is shown an exemplary sequence 614 of beaconn-tuples 610 ₁-610 _(M), where M is an integer. Each of the beaconn-tuples in the sequence 614 may be as described with respect to FIG.6C.

In operation, upon entering a beacon transmit state of operation (e.g.,at a time triggered by a real-time clock), the device 104 may read thefirst beacon n-tuple 610 ₁ and transmit a beacon comprising: datapointed to by field 612 ₃ of n-tuple 610 ₁; and fields determined byfield 612 ₃ of beacon n-tuple. The device may then listen for responsesto the beacon for the amount of time indicated in field 612 ₄ of n-tuple610 ₁. The device may repeat the beacon up to the number of times infield 612 ₅ of n-tuple 610 ₁ until a response is received or until theamount of time T_(NB) in field 612 ₆ of n-tuple 610 ₁ elapses. After aresponse is received, or T_(NB) elapses, the device 104 may read thenext n-tuple 610 ₂ in the sequence 614 and operate accordingly, that is,enter a transmit state followed by a listen state and/or a wait stateaccording to the fields of the n-tuple 610 ₂. The device 104 may repeatthis process until it has operated in accordance with each of then-tuples 610 ₁-610 _(M). After completing beacon transmission inaccordance with the last n-tuple in the sequence 614, the device mayexit the beacon transmit mode of operation or may return to the firstn-tuple in the sequence 614.

The n-tuples, sequences, and states of operation described with respectto FIGS. 6A-6D are only exemplary. Other implementations in whichchannel scan and and/or transmit operations are controlled by one ormore ordered sets of parameters will be understood from the foregoingand from inspection of the above-incorporated U.S. Provisional PatentApplication having Ser. No. 61/464,376.

FIG. 7 depicts an exemplary file system in a device comprising adynamically adaptable media access controller. The file system comprisesa scan sequence 606 ₁, a scan sequence 606 ₂, a beacon transmit sequence614 ₁, a beacon transmit sequence 614 ₂, portion 702 for storing mediaaccess control parameters, and a portion 704 for storing data. The filesystem may be, for example, the same as or similar to the indexed shortfile block (IFSB) described in the above-incorporated U.S. ProvisionalPatent Application having Ser. No. 61/464,376.

The sequences 606 ₁ and 606 ₂ may be instances of the sequence 606described in FIG. 6B. Which of the sequences 606 ₁ and 606 ₂ is utilizedfor scanning at any particular time may depend on a variety of factorssuch as, for example: where the device is located, time ofday/week/month/year, type(s) of device(s) to be communicated with,number of devices to be communicated with, types of messages to belistened for, time since last transmit and/or receive activity, etc. Inan exemplary embodiment, the sequence 606 ₁ may be utilized when thedevice is in an idle state of operation and the sequence 606 ₂ may beutilized when the device is in a hold state of operation. In anexemplary embodiment, the sequence 606 ₁ may be utilized when the deviceis operating in a first location and the sequence 606 ₂ may be utilizedwhen the device is operating in a second location

The sequences 614 ₁ and 614 ₂ may be instances of the sequence 614described in FIG. 6D. Which of the sequences 614 ₁ and 614 ₂ is utilizedfor transmitting beacons at any particular time may depend on a varietyof factors such as, for example: where the device is located, time ofday/week/month/year, type(s) of device(s) to be communicated with,number of devices to be communicated with, types of data to be sent inthe beacons, etc. In an exemplary embodiment, the sequence 606 ₁ may beutilized when transmitting beacons intended for a first type of deviceand the sequence 606 ₂ may be utilized when transmitting beaconsintended for a second type of device. In an exemplary embodiment, thesequence 606 ₁ may be utilized when transmitting beacons in a firstlocation and the sequence 606 ₂ may be utilized when transmittingbeacons in a second location.

The portion 702 may store values of one or more parameters such as, forexample, parameters which configure the congestion control module 230,the flow control module 232, the CSMA module 236, and/or the RSSI module238. Such parameters may, for example, be programmed into the portion702 by a system administrator and/or may be configured based on receivedrequest messages.

The portion 704 may store data as, for example, described with referenceto the indexed short file block (ISFB), the indexed short file seriesblock (ISFSB), and/or the generic file block (GFB) described in theabove-incorporated U.S. Provisional Patent Application having Ser. No.61/464,376.

FIG. 8 is a flowchart illustrating exemplary steps for channel scanningin a device comprising a dynamically adaptable media access controller.The exemplary steps begin with step 802 in which a scan sequence istriggered in the device 104. The scan sequence may be triggered by, forexample, a real-time clock reaching a predetermined value. In step 804,a variable i is set to 1. In step 806, the device 104 gets an n-tuple602 _(i). The n-tuple 602 _(i) may be, for example, input via theprogramming interface 222 and/or read from the memory 216. In step 808,one or more configuration registers or variables for performing achannel scan may be set to the values in the n-tuple 602 _(i). Forexample, the Channel ID for scan i may be set to value of the Channel IDfield 604 ₁ of the n-tuple 602 _(i), the scan type for scan i may be setto the value of the scan type field 604 ₂ of the n-tuple 602 _(i), thescan duration for the scan i may be set to the value of the scanduration field 604 ₃ of the n-tuple 602 _(i) and the time-to-next-scanvalue for the scan i may be set to the value of the time-to-next scanfield 604 ₄ of the n-tuple 602 _(i).

In step 810, the PHY of the device 104 may be configured according tothe Channel ID. That is, the center frequency and bandwidth of thereceiver may be configured according to the Channel ID.

In step 812, the device 104 may listen for a sync word that correspondsto the scan type of the scan i. If the scan duration elapses, and/or ifthe received signal strength on the channel being scanned goes below athreshold value (which may be configurable), without receiving the syncword, then in step 813 the device 104 may wait for the remainder ofT_(NS), which may have started counting in step 806 or 808 (e.g., if 100milliseconds have elapsed since the n-tuple 602 _(i) was retrieved, thenthe device may wait for T_(NS)−100 ms in step 813).

In step 814 it may be determined whether i has reached a maximum value.The maximum value of i may be, for example, M+1 (where M is the numberof n-tuples in the sequence 606). If i has not reached its maximumvalue, then, in step 816, i may be incremented and the steps may returnto step 806.

Returning to step 814, if i has reached its maximum value, then in step818 the scan sequence may be complete. Upon completing the scansequence, the device 104 may, for example, begin a new scan sequence,begin a beacon transmit sequence, or go into a sleep mode.

Returning to step 812, if a sync word of the type being listened for isreceived before the scan duration times out, then in step 820 the device104 will receive one or more frames and, in step 822, process thereceived frame(s). If in step 822 one or more of the received frames aredropped during MAC filtering, step 812 may be resumed.

FIG. 9 is a flowchart illustrating exemplary steps for beacontransmission by a device comprising a dynamically adaptable media accesscontroller. The exemplary steps begin with step 902 in which a beacontransmit sequence is triggered in the device 104. The scan sequence maybe triggered by, for example, a real-time clock reaching a predeterminedvalue. In step 904, a variable i is set to 1. In step 906, the device104 gets an n-tuple 610 _(i). The n-tuple 610 _(i) may be, for example,input via the programming interface 222 and/or read from the memory 216.In step 908, one or configuration registers or variables for performinga channel scan may be set to the values in the n-tuple 610 _(i). Forexample, the Channel ID for beacon i may be set to value of the ChannelID field 612 ₁ of the n-tuple 610 _(i); CSMA options for responses tobeacon i may be set to the CSMA options field 612 ₂ of the n-tuple 610_(i); the data transmitted in beacon i may be the data pointed to by thepointer field 612 ₃ of the n-tuple 610 _(i); the amount of time thedevice 104 listens for responses to beacon i may be the value in thecontention period duration (T_(C)) field 612 ₄ of the n-tuple 610 _(i);R, the maximum number of times that the device 104 repeats transmissionof the beacon i, may be set to the value of the redundancy count field612 ₅ of the n-tuple 610 _(i); and T_(NB), the time at which the device104 transmits beacon i+1 may be set to the value of thetime-to-next-beacon field 612 ₅ of the n-tuple 610 _(i). In step 912,the beacon i is transmitted onto the physical medium. In step 914, thedevice 104 may listen for a response for up to T_(C). In step 916, thevalue R may be decremented by 1 and, in step 918, if R is greater thanzero, then the steps may return to step 912.

Returning to step 918, if R is less than or equal to zero, then in step920 the device may wait for the remainder of T_(NB), which may havestarted counting in step 906 or 908 (e.g., if 100 milliseconds haveelapsed since the n-tuple 602 _(i) was retrieved, then the device maywait for T_(NB)−100 ms in step 920). In step 922, it may be determinedwhether i has reached a maximum value. The maximum value of i may be,for example, the number of n-tuples in a sequence 614. If i has notreached its maximum value and no acknowledgement was detected in step914, then, in step 924, i may be incremented and the steps may return tostep 906.

Returning to step 922, if i has reached its maximum value, then in step926 the beacon transmit sequence may be complete. Upon completing thebeacon transmit sequence, the device 104 may, for example, begin a newbeacon transmit sequence, begin a scan sequence, or go into a sleepmode.

FIGS. 10A-10C illustrate generation of parameters utilized by adynamically adaptable media access controller. A device, such as device104, may comprise a parameter generation module 1002 which may beoperable to configuring media access control in the device 104 based ona high-level input from, for example, an application or operating systemof the device 104 (e.g., via an application programming interface).

Referring to FIG. 10A, in response to a request to implement a first MACprotocol, the parameter generation module 1002 generates a set ofparameter values 1004 which may be utilized by, for example, thecongestion control module 232, the flow control module 234, and/or theCSMA module 236.

Referring to FIG. 10B, in response to a request to implement a secondMAC protocol, the parameter generation module 1002 generates a set ofparameter values 1006 which may be utilized by, for example, thecongestion control module 232, the flow control module 234, and/or theCSMA module 236.

In FIGS. 10A and 10B, the parameter values to realize the first andsecond MAC protocols were static. Some MAC protocols, however, mayrequire the periodic or continual (e.g., at or near real-time) updatingof values of the parameters. For example, in FIG. 10C, a third MACprotocol is implemented by alternating between a set of parameter values1008 and a set of parameter values 1010.

Thus, as illustrated in FIGS. 10A-10C, a variety of time and/orfrequency division multiple access protocols may be implemented in thedevice 104 simply through intelligent control of one or more parametervalues. Such protocols could include, for example, media access controlutilized in IEEE 802.11 and IEEE 802.15.4.

FIG. 11A illustrates the structure of an exemplary physical layer framecontaining a first type of data link layer protocol data unit (PDU). Thephysical layer frame comprises a preamble, a sync word, and a payload.The payload comprises a data link layer (OSI layer 2) PDU, in this case,a background frame. The background frame comprises a subnet field, abackground protocol ID (BPID) field, and CRC field. The payloadcomprises a background protocol ID (BPID) field and protocol data. Theprotocol data comprises a channel ID field and an estimated time ofarrival (ETA) field if the background protocol is the advertisingprotocol. The protocol data comprises a reservation type field and areservation duration field if the background protocol is the reservationprotocol.

FIG. 11B illustrates the structure of an exemplary physical layer framecontaining a second type of data link layer protocol data unit (PDU).The physical layer frame comprises a preamble, a sync word, and apayload. The payload comprises a data link layer (OSI layer 2) PDU, inthis case, a foreground frame. The foreground frame comprises a lengthfield, a headers field, a payload, a footer, and a cyclic redundancycheck field. The payload may comprise a network layer (OSI layer 3) PDU.The headers field comprises TxEIRP field, a subnet field, a framecontrol field, a data link layer security (DLLS) code, DLLSinitialization data, a dialog identifier, a flags field, a source ID,and a target ID. The frame control field comprises a listen flag, a DLLSflag, an enable addressing flag, a frame continuity flag, a CRC32 flag,a not mode 2 flag, and a mode 2 frame type flag. The flags fieldcomprises an addressing option flag, a virtual ID flag, a network layersecurity flag, and application flags.

FIG. 12A illustrates the structure of an exemplary first type ofnetwork-layer PDU. In FIG. 12A, the enable addressing field of the layer2 PDU indicates that the PDU contained in the payload of the layer 2 PDUis a mode 2 datastream protocol (M2DP) PDU. Specifically, the payload ofthe layer 2 PDU comprises a frame ID field and a M2DP payload.

FIG. 12B illustrates the structure of an exemplary second type ofnetwork layer PDU. In FIG. 12B, the enable addressing field of the layer2 PDU indicates that the PDU contained in the payload of the layer 2 PDUis a mode 2 network protocol (M2NP) PDU. Specifically, the payload ofthe layer 2 PDU comprises a mode 2 network layer security (M2NLS) code,M2NLS initialization data, a target address, a hop control field, a hopextension field, an origin device ID, a destination device ID, a M2NPpayload, and M2NP authentication data. The M2NP payload may contain alayer 4 PDU. The hop control field comprises hop extension flag, anOrigin ID flag, a Destination ID flag, origin/destination virtual IDflag, and a hops remaining field.

FIG. 13 depicts the structure of an exemplary transport-layer PDU. Thetransport protocol associated with the PDU in FIG. 13 is the mode 2query protocol (M2QP). The M2QP PDU (“command”) comprises a command codefield, a command control field, and may comprise one or more of a dialogtemplate, an ack template, a global query template, a local querytemplate, an error template, and a command data template. The commandcode field comprises an extension flag, a command type field, and anM2QP opcode. The command extension field comprises a collision avoidance(CA) type field, a no CSMA flag, and a no response flag. The structuresof the various templates are described with respect to FIGS. 14A-14E.

FIGS. 14A-14E depict the structure of exemplary portions of atransport-layer PDU. In FIG. 14A, the dialog template comprises aresponse timeout field, a response channel list length field, and aresponse channel list. In FIG. 14B, the ack template comprises a numberof ack fields and an ack device IDs field. In FIG. 14C, the querytemplate comprises a compare length field, a compare code field, acompare mask field, and a compare value field. The compare code fieldmay comprise a mask enable flag, a comparison type field, and acomparison parameters field. In FIG. 14D, the error template comprisesan error code field, an error subcode field, an M2QP error data field,and an extended error data field. In FIG. 14E, the command data templatecomprises one or more of a comparison template, a call template, areturn template, and command-specific data which is the data indicatedby the one or more present comparison, call, and/or return templates.The various templates of the command data template are described belowwith respect to FIGS. 15A-15F.

FIGS. 15A-15F depict the structure of exemplary portions of atransport-layer PDU. In FIG. 15A, for an M2QP opcode that indicatesfile, the comparison template comprises a comparison file ID and acomparison byte offset. In FIG. 15B, for an M2QP opcode that indicatesseries, the comparison template comprises a comparison series ID and acomparison byte offset. In FIG. 15C, for an M2QP opcode that indicatesfile, the call template comprises a max returned bytes field, a returnfile ID, and a return file entry offset. In FIG. 15D, for an M2QP opcodethat indicates series, the call template comprises a max returned bytesfield, a series ID, and a file series data offset. In FIG. 15E, for anM2QP opcode that indicates file, the return template comprises a returnfile ID, a file offset, an IFSB total length, and file data. In FIG.15F, for an M2QP opcode that indicates series, the return templatecomprises a series ID, a series length, a file series data offset, afile series total data length, one or more file IDs, one or more filelengths, and a file series data starting offset.

Additional details of the frames and fields described above with respectto FIGS. 11A-15F are described in the above-incorporated U.S.Provisional Patent Application having Ser. No. 61/464,376.

In accordance with various aspects of the present invention, anelectronic device 104 may be operable to control access to a physicalmedium (e.g., airwaves, a copper cable, or an optical fiber) utilizingcarrier sense multiple access (CSMA). The amount of time that theelectronic device 104 must sense the physical medium as being inactivebefore it permits transmission of a message onto the physical medium maybe determined based on: the size of the message, the type of themessage, the symbol rate at which the message is to be transmitted,and/or a channel onto which the message is to be transmitted. Similarly,how long and/or how many times the electronic device attempts totransmit the message may be based the size of the message, the type ofthe message, the symbol rate at which the message is to be transmitted,and/or a channel onto which the message is to be transmitted.

The message may be in response to a request received by the electronicdevice via the physical medium, and the channel onto which the messageis to be transmitted may be determined based on a field (e.g., ResponseChannel List) of the received request. The field of the received requestmay comprises a list of channels, and the electronic device 104 maysequentially listen to channels in the list until a channel meetingcertain requirements (e.g., signal strength below a threshold for atleast a period of time T_(G)′) is found or until a timeout occurs (e.g.,T_(CA) has elapsed since a CSMA process was initiated or T_(C) haselapsed since the request was sent). The maximum amount of time that theelectronic device 104 attempts to transmit the message onto the physicalmedium may be determined based on a field (e.g., Response timeout) ofthe received request message. While the message is pending transmission,a portion of the electronic device 104 may alternate between a listenstate and a wait state, wherein the amount of time in one or both of thelisten state and the wait state may be determined based on one or morefields (e.g., Response timeout and/or CA type) of the received request.Additionally or alternatively, the one or more fields of the receivedrequest may determine an equation and/or algorithm utilized by theelectronic device for the determining the amount of time spent in one orboth of the listen state and the wait state.

The electronic device 104 may comprise memory and a receiver and may beoperable to: read a series of n-tuples from the memory, each of then-tuple comprising a channel identifier, a scan duration value, and atime-to-next-scan value. For each of the read n-tuples, the device 104may be operable to: configure the receiver to receive on the channelassociated with the channel identifier for an amount of time equal tothe scan duration value; and power-down the receiver for an amount oftime equal to the time-to-next-scan value minus the scan duration value.

The electronic device 104 may comprise a memory, a transmitter, and areceiver and may be operable to read a series of n-tuples from thememory, each of the n-tuple comprising a channel identifier, acontention period value, and a time-to-next-scan value. For each of theread n-tuples, the device 104 may be operable to: configure thetransmitter to transmit a beacon on the channel associated with thechannel identifier; configure the receiver to listen for a response tothe beacon for an amount of time equal to the contention period value;and wait a period of time equal to the time-to-next-scan value minus thecontention period value before operating based on the next n-tuple inthe series of n-tuples.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for dynamicmedia access control in a multiple access system.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A system comprising: an electronic deviceoperable to control access to a physical medium utilizing carrier sensemultiple access (CSMA), wherein the amount of time that said electronicdevice must sense said physical medium as being inactive before saidelectronic device permits transmission of a message onto said physicalmedium is determined based on the size of said message.
 2. The system ofclaim 1, wherein said amount of time that said electronic device mustsense said physical medium as being inactive before said electronicdevice permits transmission of said message onto said physical medium isdetermined based on a type of said message.
 3. The system of claim 1,wherein said amount of time that said electronic device must sense saidphysical medium as being inactive before said electronic device permitstransmission of said message onto said physical medium is determinedbased on a symbol rate at which said message is to be transmitted. 4.The system of claim 1, wherein said amount of time that said electronicdevice must sense said physical medium as being inactive before saidelectronic device permits transmission of said message onto saidphysical medium is determined based on a channel onto which said messageis to be transmitted.
 5. The system of claim 1, wherein: said message isin response to a request received by said electronic device via saidphysical medium; and said channel onto which said message is to betransmitted is determined based on a field of said received request. 6.The system of claim 5, wherein: said field of said received requestcomprises a list of channels; said electronic device sequentially listento channels in said list of channels until a channel meeting certainrequirements is found or until a timeout occurs.
 7. The system of claim1, wherein: said message is in response to a request received via saidphysical medium by said electronic device; and the maximum amount oftime that said electronic device attempts to transmit said message ontosaid physical medium is determined based on a field of saidpreviously-received request message.
 8. The system of claim 1, wherein:said message is in response to a request received via said physicalmedium by said electronic device; and while said message is pendingtransmission, a portion of said electronic device alternates between alisten state and a wait state, wherein the amount of time that saidportion of said electronic device spends in one or both of said listenstate and said wait state is determined based on one or more fields ofsaid received request.
 9. The system of claim 8, wherein said one ormore fields of said received request determine an equation and/oralgorithm utilized by said electronic device for said determining saidamount of time that said portion of said electronic device spends in oneor both of said listen state and said wait state.
 10. The system ofclaim 1, wherein said electronic device comprises memory and a receiverand is operable to: read a series of n-tuples from said memory, each ofsaid n-tuple comprising a channel identifier, a scan duration value, anda time-to-next-scan value; and for each of said read n-tuples: configuresaid receiver to receive on the channel associated with said channelidentifier for an amount of time equal to said scan duration value; andpower-down said receiver for an amount of time equal to saidtime-to-next-scan value minus said scan duration value.
 11. The systemof claim 1, wherein said electronic device comprises memory, atransmitter, and a receiver and is operable to: read a series ofn-tuples from said memory, each of said n-tuple comprising a channelidentifier, a contention period value, and a time-to-next-scan value;and for each of said read n-tuples: configure said transmitter totransmit a beacon on the channel associated with said channelidentifier; configure said receiver to listen for a response to saidbeacon for an amount of time equal to said contention period value; andwait a period of time equal to said time-to-next-scan value minus saidcontention period value before operating based on the next n-tuple insaid series of n-tuples.
 12. A method comprising: in an electronicdevice which utilizes carrier sense multiple access (CSMA) forcommunicating over a physical medium: determining the amount of timethat said electronic device must sense said physical medium as beinginactive before permitting transmission of a message onto said physicalmedium based on the size of said message.
 13. The method of claim 12,wherein said determining said amount of time that said electronic devicemust sense said physical medium as being inactive before said electronicdevice permits transmission of said message onto said physical medium isbased on a type of said message.
 14. The method of claim 12, whereinsaid determining said amount of time that said electronic device mustsense said physical medium as being inactive before said electronicdevice permits transmission of said message onto said physical medium isbased on a symbol rate at which said message is to be transmitted. 15.The method of claim 12, wherein said determining said amount of timethat said electronic device must sense said physical medium as beinginactive before said electronic device permits transmission of saidmessage onto said physical medium is based on a channel onto which saidmessage is to be transmitted.
 16. The method of claim 12, wherein: saidmessage is in response to a request received by said electronic devicevia said physical medium; and said channel onto which said message is tobe transmitted is determined based on a field of said received request.17. The method of claim 16, wherein: said field of said received requestcomprises a list of channels; said electronic device sequentially listento channels in said list of channels until a channel meeting certainrequirements is found or until a timeout occurs.
 18. The method of claim12, wherein: said message is in response to a request received via saidphysical medium by said electronic device; and the maximum amount oftime that said electronic device attempts to transmit said message ontosaid physical medium is determined based on a field of saidpreviously-received request message.
 19. The method of claim 12,wherein: said message is in response to a request received via saidphysical medium by said electronic device; and while said message ispending transmission, a portion of said electronic device alternatesbetween a listen state and a wait state, wherein the amount of time thatsaid portion of said electronic device spends in one or both of saidlisten state and said wait state is determined based on one or morefields of said received request.
 20. The method of claim 19, whereinsaid one or more fields of said received request determine an equationand/or algorithm utilized by said electronic device for said determiningsaid amount of time that said portion of said electronic device spendsin one or both of said listen state and said wait state.